This middleware fixes wrong SCRIPT_NAME and PATH_INFO set by lighttpd when you mount your app under the root path ("/"). If you use lighttpd 1.4.23 or later you can instead enable fix-root-scriptname flag inside fastcgi.server instead of using this middleware.

Even with fix-root-scriptname, lighttpd still sets weird SCRIPT_NAME and PATH_INFO if you mount your application at "" or something that ends with /. Setting script_name option tells the middleware how to reconstruct the new correct SCRIPT_NAME and PATH_INFO.

If you mount the app under /something/, you should set:

enable "LighttpdScriptNameFix", script_name => "/something";

and when a request for /something/a/b?param=1 comes, SCRIPT_NAME becomes /something and PATH_INFO becomes /a/b.

script_name option is set to empty by default, which means all the request path is set to PATH_INFO and it behaves like your fastcgi application is mounted in the root path.